Optical communications – Multiplex – Optical switching
Reexamination Certificate
2001-01-30
2004-06-29
Negash, Knife-Michael (Department: 2633)
Optical communications
Multiplex
Optical switching
C398S054000, C370S390000, C370S432000, C370S465000
Reexamination Certificate
active
06757497
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
This invention relates generally to optical communication systems and, more particularly, to a multicasting optical system, characterized by high throughput and low latency network traffic, which deploys an optical signaling header propagating with the data payload to convey multicast, security and survival information, as well as information to configure a virtual optical private network.
2. Description of the Background
2.1 Overview of the Background
Recent research advances in optical Wavelength Division Multiplexing (WDM) technology have fostered the development of networks that are orders of magnitude higher in transmission bandwidth and lower in latency than existing commercial networks. While the increase in throughput and the decrease in latency are impressive, it is also necessary to provide multicasting capability combined with secure and survivable propagation as well as the capability to configure virtual optical private networks in order to realize the Next Generation Internet (NGI) vision of providing the next generation of ultra-high speed networks that can meet the requirements for supporting new applications, including national initiatives. Towards this end, current research efforts have focused on developing an ultra-low latency Internet Protocol (IP) over WDM optical packet switching technology that promises to deliver the four-fold goal of high throughput, low latency, secure and survivable networks, and optical virtual private networks. Such efforts, while promising, have yet to fully realize this four-fold goal.
The most relevant reference relating to achieving this four-fold goal is U.S. Pat. No. 6,111,673 issued to Chang and Yoo (hereinafter Chang) on Aug. 29, 2000, entitled “High-Throughput, Low-Latency Next Generation Internet Networks Using Optical-Tag Switching”, and assigned to the same assignee as the present invention. As discussed in Chang, there are a number of challenging requirements in realizing IP/WDM networks of the type required for the NGI initiative. First, the NGI network must inter-operate with the existing Internet and avoid protocol conflicts. Second, the NGI network must provide not only ultra low-latency, but must take advantage of both packet-switched (that is, bursty) IP traffic and circuit-switched WDM networks. Third, the NGI network requires no synchronization between signaling and data payload. Finally, the NGI network must accommodate data traffic of various protocols and formats so that it is possible to transmit and receive IP as well as non-IP signals without the need for complicated synchronization or format conversion.
Chang devised a methodology and concomitant network that satisfy the above requirements. As discussed in Chang, the optical packet header is carried over the same wavelength as the packet payload data. This approach eliminates the issue of header and payload synchronization. Furthermore, with a suitable use of optical delay at each intermediate optical switch, the approach also eliminates the need to estimate the initial burst delay by incorporating the optical delay directly at the switches. This approach is strikingly difference with “just-in-time” signaling in which the delay at each switch along the path needs to be known ahead of time and must be entered in the calculation for the total delay. Lastly, there is little time wasted in requesting a connection time and actually achieving a connection. In comparison to a few second delays over techniques prior to Chang, the delay is minimal, only limited by the actual hardware switching delays at each switch. The current switching technology realizes delays of only several microseconds, and shorter delays will be possible in the future. This short delay can be compensated for by using an optical fiber delay line at each network element (or, equivalently, a network node or, in short, a node) utilizing switches.
Chang utilizes a unique optical signaling header technique applicable to optical networks. Packet routing information is embedded in the same wavelength as the data payload so that both the header and data information propagate through the network with the same path and the associated delays. However, the header routing information has sufficiently different characteristics from the data payload so that the signaling header can be detected without being affected by the data payload and that the signaling header can also be stripped off without affecting the data payload. Such a unique signal routing method is overlaid onto the conventional network elements, in a modular manner, by adding two types of ‘Plug-and-Play’ modules.
As explicitly disclosed by Chang, a method for propagating a data payload from an input network element to an output network element in a wavelength division multiplexing system composed of a plurality of network elements, given that the data payload has a given format and protocol, includes the following steps: (a) generating and storing a local routing table in each of the network elements, each local routing table determining a local route through the associated one of the network elements; (b) adding an optical header to the data payload and embedded in the same wavelength as the data payload prior to inputting the data payload to the input network element, the header having a format and protocol and being indicative of the local route through each of the network elements for the data payload and the header, the format and protocol of the data payload being independent of the format and protocol of the header; (c) optically determining the header at each of the network elements as the data payload and header propagate through the WDM network; (d) selecting the local route for the data payload and the header through each of the network elements as determined by looking up the header in the corresponding local routing table; and (e) routing the data payload and the header through each of the network elements in correspondence to the selected route.
As further explicitly disclosed by Chang, the overall system is arranged in combination with (a) an electrical layer; and (b) an optical layer composed of a wavelength division multiplexing (WDM) network including a plurality of network elements, for propagating a data payload generated by a source in the electrical layer and destined for a destination in the electrical layer, the data payload having a given format and protocol. The system includes: (i) a first type of optical header module, coupling the source in the optical layer and the WDM network, for adding an optical header ahead of the data payload and embedded in the same wavelength as the data payload prior to inputting the data payload to the WDM network, the header being indicative of a local route through the network elements for the data payload and the header, the format and protocol of the data payload being independent of those of the header; and (ii) a second type of optical header module, appended to each of the network elements, for storing a local routing table in a corresponding one of the network elements, each local routing table determining a routing path through the corresponding one of the network elements, for optically determining the header at the corresponding one of the network elements as the data payload and header propagate over the WDM network, for selecting the local route for the data payload and the header through the corresponding one of the network elements as determined by looking up the header in the corresponding local routing table, and for routing the data payload and the header through the corresponding one of the network elements in correspondence to the selected route.
Chang offers numerous features and benefits including: (1) extremely low latency limited only by hardware delays; (2) high throughput and bandwidth-on-demand offered by combining multi-wavelength networking and optical label switching; (3) priority based routing which allows higher throughput for higher priority datagrams or packets; (4) scalable and modular upgrad
Chang Gee-Kung
Chowdhury Arshad M.
Ellinas Georgios
Giordano Joseph
Negash Knife-Michael
O'Banion John P.
The Regents of the University of California
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